1. Technical Field:
The invention relates to a process for recovering oil from a subterranean oil-bearing formation and more particularly to a process for cyclic flooding of an oil-bearing formation to recover oil therefrom.
2. Description of Related Art:
Water flooding is a well known method for recovering oil from subterranean oil-bearing formations. Water flooding relies primarily on an immiscible displacement mechanism to recover oil from the formation. See Elkins, L. F., et al, "Cyclic Water Flooding the Spraberry Utilizes End Effects to Increase Oil Production Rate," Journal of Petroleum Technology, August 1963, pp 877-884.
Water flooding is not an entirely satisfactory oil recovery method because in certain formations the flood channels through more permeable zones of the formation and bypasses the less permeable zones, leaving oil unrecovered therein. Polymer is commonly added to a water flood to remedy this problem. A polymer augmented water flood can improve the mobility characteristics of the flood and improve oil displacement from the less permeable zones of the formation. Unfortunately, the use of polymer substantially increases the cost of the flooding fluid. Problems attendant upon the continuous use of polymer also include reduced fluid injectivity due to the low mobility of the polymer and an increased risk of face plugging at the wellbore.
A process is needed which effectively recovers oil at a reduced material cost in comparison to conventional polymer augmented water flooding. Further, a process is needed which can mitigate injectivity problems attendant upon many conventional polymer augmented water floods.